Polishing solution and polishing method

ABSTRACT

A polishing liquid containing: abrasive grains containing a metal oxide; at least one hydroxy acid compound selected from the group consisting of a hydroxy acid having a structure represented by General Formula (A1) below and a salt thereof; and water:[In the formula, R11 represents a hydrogen atom or a hydroxy group, R12 represents a hydrogen atom, an alkyl group, or an aryl group, n11 represents an integer of 0 or more, and n12 represents an integer of 0 or more; however, a case where both of R11 and R12 are a hydrogen atom is excluded.]

TECHNICAL FIELD

The present invention relates to a polishing liquid and a polishingmethod using the same.

BACKGROUND ART

In the field of semiconductor production, with achievement of highperformance of ultra LSI devices, a miniaturization technology as anextension of the conventional technology finds restriction in allowinghigh integration and speed-up to be compatible with each other.Accordingly, while miniaturization of semiconductor elements is beingpromoted, techniques for allowing vertical high integration (namely,techniques for developing multilayered wiring) have been developed. Thistechnique is disclosed, for example, in Patent Literature 1 below.

In the process for producing a device including multilayered wiring, oneof the most important techniques is a CMP (chemical mechanicalpolishing) technique. The CMP technique is a technique in which amaterial to be polished is formed on a substrate by chemical vapordeposition (CVD) or the like to obtain a base substrate, and then thesurface of this base substrate is flattened. When the surface of thebase substrate after being flattened has irregularities, there occur,for example, such troubles that the focusing in an exposure step isprecluded, or a fine wiring structure cannot be sufficiently formed. TheCMP technique is also applied, in a production process of a device, to astep of forming an element isolation region by polishing a plasma oxidematerial (such as BPSG, HDP-SiO₂, or p-TEOS), a step of forming aninterlayer insulating material, a step of flattening a plug (forexample, Al·Cu plug) after silicon oxide is embedded in a metal wiring,or the like.

CITATION LIST Patent Literature

Patent Literature 1: U.S. Pat. No. 4,944,836

SUMMARY OF INVENTION Technical Problem

However, in a step of forming an element isolation region on thesubstrate, silicon oxide is formed by CVD or the like so as to fill agroove which have been provided in advance on the surface of thesubstrate. Thereafter, the surface of the silicon oxide is flattened byCMP to form an element isolation region. In a case where the siliconoxide is formed on the substrate of which irregularities for obtainingan element isolation region are provided on the surface, theirregularities corresponding to the irregularities of the substrate alsooccur on the surface of the silicon oxide. In the polishing of thesurface having irregularities, while a convex portion is preferentiallyremoved, a concave portion is slowly removed to flatten the surface.

For enhancing the throughput of the semiconductor production, it ispreferable that the unnecessary portion of the silicon oxide formed onthe substrate is removed as rapidly as possible. For example, in thecase of adopting shallow trench isolation (STI) in order to respond tothe achievement of the narrow width of the element isolation region, itis required that the unnecessary portion of the silicon oxide providedon the substrate is removed at a high polishing rate.

Irregularities formed on the surface of the base substrate take avariety of forms, and the widths of irregularities, which are dependenton the wiring width; the heights of irregularities; and the wiringdirections may differ according to each step or depending on the purposeof the device. However, conventionally, in the case of using the samepolishing liquid, even when one base substrate can be satisfactorilypolished, the other base substrate cannot be always satisfactorilypolished similarity in some cases. For this reason, with respect to thepolishing liquid, it is required to obtain a high polishing rate withoutdepending on a state of irregularities on a surface to be polished ofthe base substrate.

An aspect of the present invention is made to solve the above-describedproblems and provides a polishing liquid capable of obtaining a highpolishing rate without depending on a state of irregularities in thecase of polishing a surface to be polished having irregularities.Another aspect of the present invention provides a polishing methodusing the polishing liquid.

Solution to Problem

An aspect of the present invention provides a polishing liquidcontaining: abrasive grains containing a metal oxide; at least onehydroxy acid compound selected from the group consisting of a hydroxyacid having a structure represented by General Formula (A1) below and asalt thereof; and water:

[In the formula, R¹¹ represents a hydrogen atom or a hydroxy group, R¹²represents a hydrogen atom, an alkyl group, or an aryl group, n11represents an integer of 0 or more, and n12 represents an integer of 0or more; however, a case where both of R¹¹ and R¹² are a hydrogen atomis excluded.]

Another aspect of the present invention provides a polishing methodincluding a step of polishing a material to be polished by using theaforementioned polishing liquid.

According to the aforementioned polishing liquid and polishing method,it is possible to obtain a high polishing rate without depending on astate of irregularities in the case of polishing a surface to bepolished having irregularities.

Advantageous Effects of Invention

According to an aspect of the present invention, it is possible toprovide a polishing liquid capable of obtaining a high polishing ratewithout depending on a state of irregularities in the case of polishinga surface to be polished having irregularities. Furthermore, accordingto another aspect of the present invention, it is possible to provide apolishing method using the polishing liquid. These polishing liquid andpolishing method can be used for polishing an insulating material (forexample, silicon oxide) provided on a surface of a base substrate (forexample, a semiconductor wafer).

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described indetail. However, the present invention is not limited to the followingembodiment and can be modified variously within the scope of the spiritthereof and carried out.

<Definition>

In the present specification, a numerical range that has been indicatedby use of “to” indicates the range that includes the numerical valueswhich are described before and after “to”, as the minimum value and themaximum value, respectively. In the numerical ranges that are describedstepwise in the present specification, the upper limit value or thelower limit value of the numerical range of a certain stage can bearbitrarily combined with the upper limit value or the lower limit valueof the numerical range of another stage. In the numerical ranges thatare described in the present specification, the upper limit value or thelower limit value of the numerical value range may be replaced with thevalue shown in Examples. “A or B” may include either one of A and B, andmay also include both of A and B. Materials listed as examples in thepresent specification can be used singly or in combinations of two ormore, unless otherwise specifically indicated. In the presentspecification, when a plurality of substances corresponding to eachcomponent exist in the composition, the used amount of each component inthe composition means the total amount of the plurality of substancesthat exist in the composition, unless otherwise specified. In thepresent specification, the term “film” includes a structure having ashape which is formed on a part, in addition to a structure having ashape which is formed on the whole surface, when the film has beenobserved as a plan view. In the present specification, the term “step”includes not only an independent step but also a step by which anintended action of the step is achieved, even though the step cannot beclearly distinguished from other steps.

<Polishing Liquid>

A polishing liquid of the present embodiment contains abrasive grainscontaining a metal oxide, at least one hydroxy acid compound selectedfrom the group consisting of a hydroxy acid having a structurerepresented by General Formula (A1) below and a salt thereof, and water.The polishing liquid of the present embodiment can be used as a CMPpolishing liquid (polishing liquid for CMP).

[In the formula, R¹¹ represents a hydrogen atom or a hydroxy group, R¹²represents a hydrogen atom, an alkyl group, or an aryl group, n11represents an integer of 0 or more, and n12 represents an integer of 0or more; however, a case where both of R¹¹ and R¹² are a hydrogen atomis excluded.]

According to the polishing liquid of the present embodiment, a highpolishing rate can be obtained without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities, and for example, when various base substrates havingdifferent widths of irregularities on surfaces, which are dependent onthe wiring width, are polished, a high polishing rate can be obtainedwithout depending on the widths of irregularities. Such a polishingliquid is versatile and can be used in polishing of various basesubstrates with different surface states. It is speculated that theaforementioned hydroxy acid compound is likely to be strongly adsorbedto the surface of the abrasive grains containing a metal oxide andimproves the activity of the surface of the abrasive grains, and therebya high polishing rate can be obtained without depending on a state ofirregularities. However, causes obtaining the above-described effect arenot limited to this content. According to the polishing liquid of thepresent embodiment, in the case of polishing a silicon oxide surface tobe polished having irregularities, for example, a polishing rate of12000 Å/min or more can be obtained under the condition of L/S(Line/Space)=50/50 μm and a polishing rate of 190000 Å/min or more canbe obtained under the condition of L/S=20/80 μm.

Incidentally, conventionally, a high polishing rate of silicon oxide canbe achieved in the case of polishing a silicon oxide wafer that has asurface to be polished having no irregularities (a silicon oxide blanketwafer); on the other hand, a high polishing rate of silicon oxide cannotbe achieved in the case of polishing a silicon oxide wafer that has asurface to be polished having irregularities (a silicon oxide patternwafer) in some cases. On the other hand, according to the polishingliquid of the present embodiment, while a high polishing rate of aninsulating material (for example, silicon oxide) can be achieved in thecase of polishing a surface to be polished having no irregularities, ahigh polishing rate can be achieved without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities. For example, according to the polishing liquid of thepresent embodiment, in the case of polishing a silicon oxide surface tobe polished having no irregularities, a polishing rate of 3000 Å/min ormore (preferably 5000 Å/min or more, more preferably 8000 Å/min or more)can be obtained. According to the polishing liquid of the presentembodiment, a high polishing rate can be obtained in both of the case ofpolishing a surface to be polished having irregularities and the case ofpolishing a surface to be polished having no irregularities, and a highpolishing rate can be obtained without depending on the surface state(presence or absence of irregularities, a density, or the like) of thesurface to be polished. Note that, the mechanism by which silicon oxideis polished by CMP is still yet to be understood completely, and thecause of this phenomenon is as yet unknown.

Incidentally, when a polishing liquid having a high polishing rate of aninsulating material (for example, silicon oxide), the polished surfaceafter the completion of polishing is coarse and tends to be poor inflatness. Therefore, there is a case where the enhancement of theproduction efficiency is achieved by dividing the polishing treatment ofthe insulating material into two stages, and by using polishing liquidsdifferent in type from each other in the respective steps. In a firststep (coarse polishing step), a polishing liquid having a high polishingrate of the insulating material is used to remove most of the insulatingmaterial. In a second step (finishing step), the insulating material isslowly removed, and the polished surface is finished so as to besufficiently flat. In a case where the CMP with respect to an insulatingmaterial is divided into two or more stages, a high polishing rate takesprecedence over flatness in the first step, and thus a lower polishingrate may result in lower productivity. On the other hand, according tothe polishing liquid of the present embodiment, since a high polishingrate can be obtained without depending on a state of irregularities,even in a case where the CMP with respect to an insulating material (forexample, silicon oxide) is divided into two or more stages, a decreasein productivity can be suppressed.

(Abrasive Grains)

The abrasive grains contain a metal oxide. The metal oxide can containcerium oxide (ceria), alumina, silica, titania, zirconia, magnesia,mullite, or the like. The constituent components of the abrasive grainscan be used singly or in combination of two or more types thereof. Theabrasive grains preferably contain cerium oxide from the viewpoint ofeasily obtaining a high polishing rate without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities.

The polishing liquid using the abrasive grains containing cerium oxidehas a feature that polishing scratches occurring on the polished surfaceare relatively small in number. Conventionally, from the viewpoint ofeasily achieving a high polishing rate of a material to be polished (forexample, an insulating material such as silicon oxide), a polishingliquid containing silica particles as the abrasive grains has beenwidely used. However, the polishing liquid using silica particlesgenerally has a problem in that polishing scratches easily occur on thepolished surface. In a device having fine patterns since the generationof 45 nm in wire width, even fine scratches having hitherto caused noproblems may affect the reliability of the device.

In the case of using cerium oxide, it is preferable that the abrasivegrains contain polycrystalline cerium oxide having a crystal grainboundary (for example, polycrystalline cerium oxide having multiplecrystallites surrounded by crystal grain boundaries). It is consideredthat the polycrystalline cerium oxide particle having such aconfiguration is different from a simple aggregate in which singlecrystal particles aggregate, is made fine by the stress duringpolishing, and at the same time allows active surfaces (the surfaces notexposed to outside before being made fine) to appear one after another,so that a high polishing rate of a material to be polished (for example,an insulating material such as silicon oxide) can be highly maintained.Such a polycrystalline cerium oxide particle is described in detail, forexample, in International Publication WO 99/31195.

The method for producing abrasive grains containing cerium oxide is notparticularly limited, and examples thereof include liquid phasesynthesis; and a method performing oxidation by firing or hydrogenperoxide or the like. In the case of obtaining abrasive grainscontaining the above-described polycrystalline cerium oxide having acrystal grain boundary, a method in which a cerium source such as ceriumcarbonate is fired is preferred. The temperature during theabove-described firing is preferably 350° C. to 900° C. In a case wherethe produced cerium oxide particles aggregate, it is preferable tomechanically pulverize. The pulverizing method is not particularlylimited, but for example, dry pulverization with a jet mill or the like;and wet pulverization with a planetary bead mill or the like arepreferred. The jet mill is described, for example, in “Kagaku KogakuRonbunshu (Chemical Industrial Paper Collection)”, Vol. 6, No. 5 (1980),pp. 527 to 532.

The abrasive grains may contain constituent components other than themetal oxide. Examples of the constituent components other than the metaloxide include a cerium-based compound (excluding cerium oxide), siliconnitride, α-sialon, aluminum nitride, titanium nitride, silicon carbide,and boron carbide. Examples of the cerium-based compound include ceriumhydroxide, cerium ammonium nitrate, cerium acetate, cerium sulfatehydrate, cerium bromate, cerium bromide, cerium chloride, ceriumoxalate, cerium nitrate, and cerium carbonate.

The lower limit of the content of the metal oxide (for example, ceriumoxide) in the abrasive grains is preferably 50% by mass or more, morepreferably 70% by mass or more, further preferably 90% by mass or more,particularly preferably 95% by mass or more, extremely preferably 97% bymass or more, and highly preferably 99% by mass or more, based on thetotal mass of the abrasive grains (the total mass of the abrasive grainscontained in the polishing liquid), from the viewpoint of easilyobtaining a high polishing rate of silicon oxide. The abrasive grainscontaining a metal oxide may be an embodiment which is substantiallycomposed of a metal oxide (an embodiment in which substantially 100% bymass of the abrasive grains is a metal oxide). The abrasive grains maybe an embodiment not containing zirconia.

The lower limit of the average particle diameter of the abrasive grainsis preferably 50 nm or more, more preferably 70 nm or more, furtherpreferably 80 nm or more, and particularly preferably 90 nm or more,from the viewpoint of easily obtaining a high polishing rate of amaterial to be polished (for example an insulating material such assilicon oxide). The upper limit of the average particle diameter of theabrasive grains is preferably 500 nm or less, more preferably 300 nm orless, further preferably 280 nm or less, particularly preferably 250 nmor less, extremely preferably 200 nm or less, highly preferably 180 nmor less, even more preferably 150 nm or less, further preferably 120 nmor less, and particularly preferably 100 nm or less, from the viewpointof easily suppressing polishing scratches. From these viewpoints, theaverage particle diameter of the abrasive grains is preferably 50 to 500nm.

In order to control the average particle diameter of the abrasivegrains, conventionally known methods can be used. By taking the ceriumoxide particles as an example, examples of the method of controlling theaverage particle diameter of the abrasive grains include the control ofthe firing temperature, the firing time, the pulverization condition, orthe like mentioned above; and the application of filtration,classification, or the like. As the average particle diameter of theabrasive grains, an arithmetic average diameter obtained by measuring apolishing liquid sample having abrasive grains dispersed therein by alaser diffraction/scattering type particle size distribution analyzercan be used. The average particle diameter of the abrasive grains is avalue that is measured, for example, using LA-920 (trade name)manufactured by HORIBA, Ltd. or the like.

The zeta potential (surface potential) of the abrasive grains in thepolishing liquid is preferably positive (the zeta potential is more than0 mV) from the viewpoint of easily obtaining a high polishing ratewithout depending on a state of irregularities in the case of polishinga surface to be polished having irregularities. The lower limit of thezeta potential of the abrasive grains is preferably 10 mV or more, morepreferably 20 mV or more, further preferably 30 mV or more, particularlypreferably 40 mV or more, extremely preferably 50 mV or more, and highlypreferably 60 mV or more, from the viewpoint of easily obtaining a highpolishing rate without depending on a state of irregularities in thecase of polishing a surface to be polished having irregularities. Theupper limit of the zeta potential of the abrasive grains is preferably200 mV or less, more preferably 150 mV or less, further preferably 100mV or less, particularly preferably 80 mV or less, and extremelypreferably 70 mV or less. From these viewpoints, the zeta potential ofthe abrasive grains is preferably more than 0 mV and 200 mV or less,more preferably 10 to 200 mV, and further preferably 30 to 70 mV. Thezeta potential of the abrasive grains can be measured, for example, byusing a dynamic light scattering type zeta potential measurementapparatus (for example, trade name: DelsaNano C manufactured by BeckmanCoulter, Inc.).

The content of the abrasive grains is preferably in the following rangebased on the total mass of the polishing liquid. The lower limit of thecontent of the abrasive grains is preferably 0.01% by mass or more, morepreferably 0.05% by mass or more, further preferably 0.10% by mass ormore, particularly preferably more than 0.10% by mass, extremelypreferably 0.15% by mass or more, highly preferably 0.18% by mass ormore, even more preferably more than 0.18% by mass, further preferably0.20% by mass or more, particularly preferably 0.25% by mass or more,extremely preferably more than 0.25% by mass, highly preferably 0.30% bymass or more, even more preferably 0.50% by mass or more, furtherpreferably 0.70% by mass or more, particularly preferably 0.90% by massor more, and extremely preferably 0.95% by mass or more, from theviewpoint of easily achieving a high polishing rate. The upper limit ofthe content of the abrasive grains is preferably 10% by mass or less,more preferably 5.0% by mass or less, further preferably 3.0% by mass orless, particularly preferably 2.0% by mass or less, extremely preferably1.5% by mass or less, and highly preferably 1.0% by mass or less, fromthe viewpoint of easily suppressing the aggregation of the abrasivegrains and the viewpoint of easily achieving a high polishing rate. Fromthese viewpoints, the content of the abrasive grains is preferably 0.01to 10% by mass, more preferably 0.10 to 10% by mass, and furtherpreferably 0.10 to 3.0% by mass.

(Hydroxy Acid Compound)

The polishing liquid of the present embodiment contains at least onehydroxy acid compound (hereinafter, referred to as “specific hydroxyacid compound”) selected from the group consisting of a hydroxy acidhaving a structure represented by General Formula (A1) below and a saltthereof. The hydroxy acid is carboxylic acid having a hydroxy group.

[In the formula, R¹¹ represents a hydrogen atom or a hydroxy group, R¹²represents a hydrogen atom, an alkyl group, or an aryl group, n11represents an integer of 0 or more, and n12 represents an integer of 0or more; however, a case where both of R¹¹ and R¹² are a hydrogen atomis excluded.]

Examples of the salt of the hydroxy acid having a structure representedby General Formula (A1) include a salt in which the hydrogen atom of acarboxyl group is substituted with an alkali metal (for example, asodium atom). The polishing liquid of the present embodiment may or maynot contain a hydroxy acid compound other than the specific hydroxy acidcompound.

The specific hydroxy acid compound preferably satisfies at least one ofthe following features from the viewpoint of easily obtaining a highpolishing rate without depending on a state of irregularities in thecase of polishing a surface to be polished having irregularities.

The number of carbon atoms of the alkyl group for R¹² is preferably 0 to3, more preferably 0 to 2, and further preferably 1 or 2.

The aryl group for R¹² is preferably a phenyl group.

n11 is preferably 0 to 3, more preferably 0 to 2, and further preferably0 or 1.

n12 is preferably 0 to 3, more preferably 0 to 2, further preferably 0or 1, and particularly preferably 1.

The specific hydroxy acid compound preferably has a branched carbonchain.

The specific hydroxy acid compound preferably has no polyoxyalkylenegroup (for example, a polyoxyethylene group).

The specific hydroxy acid compound is preferably at least one selectedfrom the group consisting of a hydroxy acid having a molecular weight of90 to 200 and a salt thereof. The lower limit of the molecular weight ispreferably 95 or more, more preferably 100 or more, further preferablymore than 100, particularly preferably 102 or more, and extremelypreferably 104 or more. The upper limit of the molecular weight ispreferably 180 or less, more preferably 170 or less, further preferably160 or less, and particularly preferably 150 or less.

The specific hydroxy acid compound preferably contains at least oneselected from the group consisting of a hydroxy acid having a structurerepresented by General Formula (A2) below and a salt thereof and ahydroxy acid having a structure represented by General Formula (A3)below and a salt thereof, from the viewpoint of easily obtaining a highpolishing rate without depending on a state of irregularities in thecase of polishing a surface to be polished having irregularities.

[In the formula, R²¹ and R²² each independently represent a hydrogenatom, an alkyl group, or an aryl group, and the total number of carbonatoms of R²¹ and R²² is 2 or more.]

[In the formula, R³ represents a hydrogen atom, an alkyl group, or anaryl group, n31 represents an integer of 0 to 2, and n32 represents aninteger of 0 or more.]

The structure represented by General Formula (A2) preferably satisfiesat least one of the following features from the viewpoint of easilyobtaining a high polishing rate without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities.

The number of carbon atoms of the alkyl group for R²¹ is preferably 0 to3, more preferably 0 to 2, and further preferably 1 or 2.

The aryl group for R²¹ is preferably a phenyl group.

The total number of carbon atoms of R²¹ and R²² is preferably 2 to 9,more preferably 2 to 6, and further preferably 2 to 4.

The structure represented by General Formula (A3) preferably satisfiesat least one of the following features from the viewpoint of easilyobtaining a high polishing rate without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities.

R³ is preferably a hydrogen atom or an alkyl group.

The number of carbon atoms of the alkyl group for R³ is preferably 0 to3, more preferably 0 to 2, and further preferably 1 or 2.

n31 is preferably 0 or 1.

n32 is preferably 0 to 3, more preferably 0 to 2, further preferably 0or 1, and particularly preferably 1.

From the viewpoint of easily obtaining a high polishing rate withoutdepending on a state of irregularities in the case of polishing asurface to be polished having irregularities and the viewpoint of easilyachieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities, thespecific hydroxy acid compound preferably contains at least one selectedfrom the group consisting of glyceric acid, mandelic acid,2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyricacid, and hydroxyisobutyric acid, more preferably contains at least oneselected from the group consisting of glyceric acid,2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyricacid, and hydroxyisobutyric acid, and further preferably contains atleast one selected from the group consisting of2,2-bis(hydroxymethyl)butyric acid and hydroxyisobutyric acid. Examplesof hydroxyisobutyric acid include 2-hydroxyisobutyric acid (also knownas 2-methyllactic acid) and 3-hydroxyisobutyric acid.

The lower limit of the content of the specific hydroxy acid compound ispreferably 50% by mass or more, more preferably 70% by mass or more,further preferably 90% by mass or more, particularly preferably 95% bymass or more, extremely preferably 97% by mass or more, and highlypreferably 99% by mass or more, based on the total mass of a hydroxyacid compound (a hydroxy acid compound contained in the polishing liquidof the present embodiment), from the viewpoint of easily obtaining ahigh polishing rate without depending on a state of irregularities inthe case of polishing a surface to be polished having irregularities andthe viewpoint of easily achieving a high polishing rate of silicon oxidein the case of polishing a surface to be polished having noirregularities. The hydroxy acid compound contained in the polishingliquid of the present embodiment may be an embodiment which issubstantially composed of the specific hydroxy acid compound (anembodiment in which substantially 100% by mass of the hydroxy acidcompound contained in the polishing liquid of the present embodiment isthe specific hydroxy acid compound).

The content of the specific hydroxy acid compound is preferably in thefollowing range based on the total mass of an acid component (an acidcomponent contained in the polishing liquid of the present embodiment),from the viewpoint of easily obtaining a high polishing rate withoutdepending on a state of irregularities in the case of polishing asurface to be polished having irregularities and the viewpoint of easilyachieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities. The lowerlimit of the content of the specific hydroxy acid compound is preferably5% by mass or more, more preferably 10% by mass or more, furtherpreferably more than 10% by mass, particularly preferably 15% by mass ormore, extremely preferably more than 15% by mass, and highly preferably20% by mass or more. The upper limit of the content of the specifichydroxy acid compound is preferably 90% by mass or less, more preferably85% by mass or less, further preferably 80% by mass or less,particularly preferably 75% by mass or less, and extremely preferably70% by mass or less. From these viewpoints, the content of the specifichydroxy acid compound is preferably 5 to 90% by mass. The lower limit ofthe content of the specific hydroxy acid compound is preferably morethan 20% by mass, more preferably 30% by mass or more, furtherpreferably 30% by mass or more, particularly preferably 40% by mass ormore, and extremely preferably 50% by mass or more, based on the totalmass of the acid component, from the viewpoint of easily obtaining aparticularly high polishing rate without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities.

The content of the specific hydroxy acid compound is preferably in thefollowing range based on the total mass of the polishing liquid, fromthe viewpoint of easily obtaining a high polishing rate withoutdepending on a state of irregularities in the case of polishing asurface to be polished having irregularities and the viewpoint of easilyachieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities. The lowerlimit of the content of the specific hydroxy acid compound is preferably0.01% by mass or more, more preferably 0.03% by mass or more, furtherpreferably 0.05% by mass or more, particularly preferably 0.06% by massor more, extremely preferably 0.07% by mass or more, and highlypreferably 0.075% by mass or more. The upper limit of the content of thespecific hydroxy acid compound is preferably 10% by mass or less, morepreferably 5.0% by mass or less, further preferably 3.0% by mass orless, particularly preferably 1.0% by mass or less, extremely preferably0.80% by mass or less, highly preferably 0.70% by mass or less, evenmore preferably 0.60% by mass or less, further preferably 0.50% by massor less, particularly preferably 0.40% by mass or less, extremelypreferably less than 0.40% by mass, and highly preferably 0.30% by massor less. From these viewpoints, the content of the specific hydroxy acidcompound is preferably 0.01 to 10% by mass and more preferably 0.01 to1.0% by mass.

The lower limit of the content of the specific hydroxy acid compound ispreferably 0.08% by mass or more, more preferably 0.10% by mass or more,further preferably more than 0.10% by mass, particularly preferably0.15% by mass or more, extremely preferably 0.20% by mass or more,highly preferably 0.25% by mass or more, and even more preferably 0.30%by mass or more, based on the total mass of the polishing liquid, fromthe viewpoint of easily obtaining a particularly high polishing ratewithout depending on a state of irregularities in the case of polishinga surface to be polished having irregularities. The upper limit of thecontent of the specific hydroxy acid compound is preferably 0.25% bymass or less, more preferably 0.20% by mass or less, further preferably0.15% by mass or less, particularly preferably 0.10% by mass or less,extremely preferably less than 0.10% by mass, highly preferably 0.08% bymass or less, and even more preferably 0.075% by mass or less, based onthe total mass of the polishing liquid, from the viewpoint of easilyachieving a particularly high polishing rate of silicon oxide in thecase of polishing a surface to be polished having no irregularities.

A ratio A1 of the content of the hydroxy acid compound (the total amountof the hydroxy acid compound contained in the polishing liquid of thepresent embodiment) with respect to the content of the abrasive grains(the content of the hydroxy acid compound/the content of the abrasivegrains) and/or a ratio A2 of the content of the specific hydroxy acidcompound with respect to the content of the abrasive grains (the contentof the specific hydroxy acid compound/the content of the abrasivegrains) is preferably in the following range (hereinafter, the ratio A1and the ratio A2 are referred to as “ratio A”), from the viewpoint ofeasily obtaining a high polishing rate without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities and the viewpoint of easily achieving a high polishingrate of silicon oxide in the case of polishing a surface to be polishedhaving no irregularities. The lower limit of the ratio A is preferably0.01 or more, more preferably 0.03 or more, further preferably 0.05 ormore, particularly preferably 0.06 or more, extremely preferably 0.07 ormore, and highly preferably 0.075 or more. The upper limit of the ratioA is preferably 10 or less, more preferably 5.0 or less, furtherpreferably 3.0 or less, particularly preferably 1.0 or less, extremelypreferably 0.80 or less, highly preferably 0.70 or less, even morepreferably 0.60 or less, further preferably 0.50 or less, particularlypreferably 0.40 or less, extremely preferably less than 0.40, and highlypreferably 0.30 or less. From these viewpoints, the ratio A ispreferably 0.01 to 10.

The lower limit of the ratio A is preferably 0.08 or more, morepreferably 0.10 or more, further preferably more than 0.10, particularlypreferably 0.15 or more, extremely preferably 0.20 or more, highlypreferably 0.25 or more, and even more preferably 0.30 or more, from theviewpoint of easily obtaining a particularly high polishing rate withoutdepending on a state of irregularities in the case of polishing asurface to be polished having irregularities. The upper limit of theratio A is preferably 0.25 or less, more preferably 0.20 or less,further preferably 0.15 or less, particularly preferably 0.10 or less,extremely preferably less than 0.10, highly preferably 0.08 or less, andeven more preferably 0.075 or less, from the viewpoint of easilyachieving a particularly high polishing rate of silicon oxide in thecase of polishing a surface to be polished having no irregularities.

(Other Components)

The polishing liquid of the present embodiment may further contain otheradditives (excluding the abrasive grains and the hydroxy acid compound).Examples of the additives include an acid component other than thehydroxy acid compound; an alkali component; a water-soluble polymer; anda nonionic surfactant. The acid component and the alkali component canbe used as a pH adjusting agent for adjusting pH. The polishing liquidof the present embodiment may contain a buffering agent for stabilizingpH. A buffering agent may be added as a buffer solution (a liquidcontaining a buffering agent). Examples of the buffer solution includean acetate buffer solution and a phthalate buffer solution.

The polishing liquid of the present embodiment may contain at least oneamino acid component selected from the group consisting of an amino acidand an amino acid derivative, as an acid component other than thehydroxy acid compound. Examples of the amino acid derivatives includeamino acid esters, amino acid salts, and peptides. The amino acid is acompound having both functional groups of an amino group and a carboxylgroup.

Examples of the amino acid component include glycine, α-alanine,β-alanine (also known as 3-aminopropanoic acid), 2-aminobutyric acid,norvaline, valine, leucine, norleucine, isoleucine, alloisoleucine,phenylalanine, proline, sarcosine, ornithine, lysine, serine, threonine,allothreonine, homoserine, tyrosine, 3,5-diiodotyrosine,β(3,4-dihydroxyphenyl)-alanine, thyroxin, 4-hydroxy-proline, cysteine,methionine, ethionine, lanthionine, cystathionine, cystine, cysteicacid, aspartic acid, glutamic acid, S-(carboxymethyl)-cysteine,4-aminobutyric acid, asparagine, glutamine, azaserine, arginine,canavanine, citrulline, δ-hydroxy-lysine, creatine, kynurenine,histidine, 1-methyl-histidine, 3-methyl-histidine, ergothioneine,tryptophan, glycylglycine, glycylglycylglycine, vasopressin, oxytocin,Kassinin, eledoisin, glucagon, secretin, proopiomelanocortin,enkephalin, and prodynorphin.

The amino acid component preferably contains a low-molecular-weightamino acid from the viewpoint of easily suppressing the aggregation ofthe abrasive grains (such as cerium oxide particles). The molecularweight of the amino acid component is preferably 300 or less, morepreferably 250 or less, and further preferably 200 or less. Examples ofsuch an amino acid include glycine (molecular weight: 75), α-alanine(molecular weight: 89), β-alanine (molecular weight: 89), serine(molecular weight: 105), histidine (molecular weight: 155),glycylglycine (molecular weight: 132), and glycylglycylglycine(molecular weight: 189). The amino acid component preferably containsglycine from the viewpoint of easily obtaining a high polishing ratewithout depending on a state of irregularities in the case of polishinga surface to be polished having irregularities and the viewpoint ofeasily achieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities.

The content of the acid component (for example, an amino acid component)other than the hydroxy acid compound is preferably in the followingrange based on the total mass of the polishing liquid. The lower limitof the content of the acid component other than the hydroxy acidcompound is preferably 0.005% by mass or more, more preferably 0.01% bymass or more, further preferably 0.02% by mass or more, particularlypreferably 0.03% by mass or more, extremely preferably 0.05% by mass ormore, highly preferably 0.10% by mass or more, and even more preferably0.20% by mass or more, from the viewpoint of easily achieving asufficiently high polishing rate of silicon oxide. The upper limit ofthe content of the acid component other than the hydroxy acid compoundis preferably 10% by mass or less, more preferably 5.0% by mass or less,further preferably 3.0% by mass or less, particularly preferably 1.0% bymass or less, extremely preferably 0.50% by mass or less, and highlypreferably 0.40% by mass or less, from the viewpoint of easily achievinga sufficiently high polishing rate of silicon oxide. From theseviewpoints, the content of the acid component other than the hydroxyacid compound is preferably 0.005 to 10% by mass.

A ratio B1 of the content of the amino acid component with respect tothe content of the hydroxy acid compound (the total amount of thehydroxy acid compound contained in the polishing liquid of the presentembodiment) (the content of the amino acid component/the content of thehydroxy acid compound), and/or a ratio B2 of the content of the aminoacid component with respect to the content of the specific hydroxy acidcompound (the content of the amino acid component/the content of thespecific hydroxy acid compound) is preferably in the following range(hereinafter, the ratio B1 and the ratio B2 are referred to as “ratioB”), from the viewpoint of easily obtaining a high polishing ratewithout depending on a state of irregularities in the case of polishinga surface to be polished having irregularities and the viewpoint ofeasily achieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities. The lowerlimit of the ratio B is preferably 0.01 or more, more preferably 0.05 ormore, further preferably 0.10 or more, particularly preferably 0.30 ormore, and extremely preferably 0.50 or more. The upper limit of theratio B is preferably 10 or less, more preferably 8.0 or less, furtherpreferably 5.0 or less, and particularly preferably 4.0 or less. Fromthese viewpoints, the ratio B is preferably 0.01 to 10. The upper limitof the ratio B is preferably 3.0 or less, more preferably 2.0 or less,further preferably 1.5 or less, and particularly preferably 1.0 or less,from the viewpoint of easily obtaining a particularly high polishingrate without depending on a state of irregularities in the case ofpolishing a surface to be polished having irregularities.

Examples of the alkali component include heterocyclic amine,alkanolamine, ammonia, sodium hydroxide, and tetramethylammoniumhydroxide (TMAH). The polishing liquid of the present embodiment may notcontain an alkali component.

The heterocyclic amine is an amine having at least one heterocyclicring. Examples of the heterocyclic amine include pyrrolidine, pyrrole,imidazole, pyrazole, oxazole, thiazole, pyridine, pyrazine, pyrimidine,pyridazine, triazine, tetrazine, and derivatives thereof (compoundshaving skeletons of these compounds as skeletons).

As the derivatives, aminothiazole, dialkylpyrazole (for example,dimethylpyrazole such as 3,5-dialkylpyrazole), or the like can be used.The heterocyclic amine preferably contains at least one selected fromthe group consisting of aminothiazole and dialkylpyrazole (for example,dimethylpyrazole such as 3,5-dialkylpyrazole), from the viewpoint ofeasily obtaining a high polishing rate without depending on a state ofirregularities in the case of polishing a surface to be polished havingirregularities and the viewpoint of easily achieving a high polishingrate of silicon oxide in the case of polishing a surface to be polishedhaving no irregularities.

The content of the heterocyclic amine is preferably in the followingrange based on the total mass of the polishing liquid. The lower limitof the content of the heterocyclic amine is preferably 0.001% by mass ormore, more preferably 0.005% by mass or more, and further preferably0.01% by mass or more, from the viewpoint of easily achieving asufficiently high polishing rate of silicon oxide. The upper limit ofthe content of the heterocyclic amine is preferably 10% by mass or less,more preferably 5.0% by mass or less, further preferably 3.0% by mass orless, particularly preferably 1.0% by mass or less, extremely preferably0.50% by mass or less, and highly preferably 0.30% by mass or less, fromthe viewpoint of easily achieving a sufficiently high polishing rate ofsilicon oxide. From these viewpoints, the content of the heterocyclicamine is preferably 0.001 to 10% by mass.

The alkanolamine is a compound having a hydroxy group and an amino groupbonded to an alkane skeleton. Examples of the alkanolamine includemethanolamine, ethanolamine, diethanolamine, triethanolamine,propanolamine, dimethylethanolamine, N-methylethanolamine,N-polyoxypropylene ethylenediamine, aminoethylethanolamine, heptaminol,isoetharine, and sphingosine.

The content of the alkanolamine is preferably in the following rangebased on the total mass of the polishing liquid. The lower limit of thecontent of the alkanolamine is preferably 0.001% by mass or more, morepreferably 0.005% by mass or more, and further preferably 0.01% by massor more, from the viewpoint of easily achieving a sufficiently highpolishing rate of silicon oxide. The upper limit of the content of thealkanolamine is preferably 10% by mass or less, more preferably 5.0% bymass or less, further preferably 3.0% by mass or less, particularlypreferably 1.0% by mass or less, extremely preferably 0.50% by mass orless, and highly preferably 0.30% by mass or less, from the viewpoint ofeasily achieving a sufficiently high polishing rate of silicon oxide.From these viewpoints, the content of the alkanolamine is preferably0.001 to 10% by mass.

Examples of the water-soluble polymer include polyacrylic acid-basedpolymers such as polyacrylic acid, a polyacrylic acid copolymer,polyacrylate, and a polyacrylic acid copolymer salt; polymethacrylicacid-based polymers such as polymethacrylic acid and polymethacrylate;polyacrylamide; polydimethylacrylamide; polysaccharides such as alginicacid, pectinic acid, carboxymethylcellulose, agar, curdlan, dextrin,cyclodextrin, and pullulan; vinyl-based polymers such as polyvinylalcohol, polyvinylpyrrolidone, and polyacrolein; glycerin-based polymerssuch as polyglycerin and polyglycerin derivatives; and polyethyleneglycol.

The polishing liquid of the present embodiment may not contain awater-soluble polymer. The polishing liquid of the present embodimentmay not contain a water-soluble polymer. For example, the polishingliquid of the present embodiment may not contain at least one selectedfrom the group consisting of polyvinyl alcohol, polyvinylpyrrolidone,polyglycerol, and polyethylene glycol.

Examples of the nonionic surfactant include ether-type surfactants suchas polyoxypropylene polyoxyethylene alkyl ether, polyoxyethylene alkylether, polyoxyethylene alkylaryl ether, polyoxyethylene polyoxypropyleneether derivatives, polyoxypropylene glyceryl ether, oxyethylene adductsof polyethylene glycol, oxyethylene adducts of methoxypolyethyleneglycol, oxyethylene adducts of acethylene-based diols; ester-typesurfactants such as sorbitan fatty acid ester and glycerol borate fattyacid ester; amino ether-type surfactants such as polyoxyethylenealkylamine; ether ester-type surfactants such as polyoxyethylenesorbitan fatty acid ester, polyoxyethylene glycerol borate fatty acidester, and polyoxyethylene alkyl ester; alkanolamide-type surfactantssuch as fatty acid alkanolamide and polyoxyethylene fatty acidalkanolamide; oxyethylene adducts of acetylene-based diols;polyvinylpyrrolidone; polyacrylamide; polydimethylacrylamide; andpolyvinyl alcohol. The polishing liquid of the present embodiment maynot contain a nonionic surfactant.

The upper limit of the content of the polymer compound having a hydroxygroup in the polishing liquid of the present embodiment may be less than0.01% by mass, 0.005% by mass or less, 0.001% by mass or less, 0.0001%by mass or less, or less than 0.0001% by mass, based on the total massof the polishing liquid. The polishing liquid of the present embodimentmay not contain a polymer compound having a hydroxy group.

The upper limit of the content of the polymer compound having an amidegroup in the polishing liquid of the present embodiment may be less than0.01% by mass, 0.005% by mass or less, 0.001% by mass or less, 0.0001%by mass or less, or less than 0.0001% by mass, based on the total massof the polishing liquid. The polishing liquid of the present embodimentmay not contain a polymer compound having an amide group. For example,the polishing liquid of the present embodiment may not containpoly-N-vinylacetamide.

The upper limit of the content of the compound having a cyclic structure(for example, a compound having two or more cyclic structures) in thepolishing liquid of the present embodiment may be less than 0.01% bymass, 0.005% by mass or less, 0.001% by mass or less, less than 0.001%by mass, 0.0001% by mass or less, or less than 0.0001% by mass, based onthe total mass of the polishing liquid. The polishing liquid of thepresent embodiment may not contain a compound having a cyclic structure(for example, a compound having two or more cyclic structures).

The upper limit of the content of a compound having a polyalkylene chainin the polishing liquid of the present embodiment may be less than 0.01%by mass, 0.005% by mass or less, 0.001% by mass or less, 0.0001% by massor less, or less than 0.0001% by mass, based on the total mass of thepolishing liquid. The polishing liquid of the present embodiment may notcontain a compound having a polyalkylene chain.

The upper limit of the content of a water-soluble polyamide in thepolishing liquid of the present embodiment may be less than 0.0001% bymass based on the total mass of the polishing liquid. The polishingliquid of the present embodiment may not contain a water-solublepolyamide.

The upper limit of the content of an azo compound (for example, an azoderivative) in the polishing liquid of the present embodiment may beless than 0.025% by mass, 0.02% by mass or less, 0.01% by mass or less,0.005% by mass or less, 0.001% by mass or less, 0.0001% by mass or less,or less than 0.0001% by mass, based on the total mass of the polishingliquid. The polishing liquid of the present embodiment may not containan azo compound (for example, an azo derivative).

The upper limit of the content of an oxidizing agent in the polishingliquid of the present embodiment may be less than 0.003 mol/L or 0.001mol/L or less, based on the entire polishing liquid. The polishingliquid of the present embodiment may not contain an oxidizing agent.

(Water)

The polishing liquid of the present embodiment contains water. Examplesof water include deionized water and ultrapure water. The content ofwater is not particularly limited, and may be the remainder of thepolishing liquid excluding the content of the other constituentcomponents.

The total amount of the abrasive grains and water is preferably in thefollowing range based on the total mass of the polishing liquid, fromthe viewpoint of easily obtaining a high polishing rate withoutdepending on a state of irregularities in the case of polishing asurface to be polished having irregularities and the viewpoint of easilyachieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities. The lowerlimit of the total amount of the abrasive grains and water is preferably95% by mass or more, more preferably 96% by mass or more, furtherpreferably 97% by mass or more, particularly preferably 98% by mass ormore, extremely preferably 99% by mass or more, highly preferably morethan 99% by mass, even more preferably 99.1% by mass or more, furtherpreferably 99.2% by mass or more, particularly preferably 99.3% by massor more, and extremely preferably 99.4% by mass or more. The upper limitof the total amount of the abrasive grains and water is preferably lessthan 100% by mass, more preferably 99.9% by mass or less, and furtherpreferably 99.8% by mass or less. From these viewpoints, the totalamount of the abrasive grains and water is preferably 95% by mass ormore and less than 100% by mass. The total amount of the abrasive grainsand water is preferably more than 99.4% by mass, more preferably 99.5%by mass or more, and further preferably 99.6% by mass or more, from theviewpoint of easily achieving a particularly high polishing rate ofsilicon oxide in the case of polishing a surface to be polished havingno irregularities.

The total amount of the hydroxy acid compound and water is preferably inthe following range based on the total mass of the polishing liquid,from the viewpoint of easily obtaining a high polishing rate withoutdepending on a state of irregularities in the case of polishing asurface to be polished having irregularities and the viewpoint of easilyachieving a high polishing rate of silicon oxide in the case ofpolishing a surface to be polished having no irregularities. The lowerlimit of the total amount of the hydroxy acid compound and water ispreferably 95% by mass or more, more preferably 96% by mass or more,further preferably 97% by mass or more, particularly preferably 98% bymass or more, extremely preferably 98.2% by mass or more, highlypreferably 98.4% by mass or more, even more preferably 98.6% by mass ormore, and further preferably 98.7% by mass or more. The upper limit ofthe total amount of the hydroxy acid compound and water is preferablyless than 100% by mass, more preferably 99.8% by mass or less, furtherpreferably 99.5% by mass or less, particularly preferably 99.2% by massor less, extremely preferably 99% by mass or less, and highly preferablyless than 99% by mass. From these viewpoints, the total amount of thehydroxy acid compound and water is preferably 95% by mass or more andless than 100% by mass.

The lower limit of the total amount of the abrasive grains, the hydroxyacid compound, and water is preferably 95% by mass or more, morepreferably 96% by mass or more, further preferably 97% by mass or more,particularly preferably 98% by mass or more, extremely preferably 99% bymass or more, highly preferably 99.2% by mass or more, even morepreferably 99.4% by mass or more, further preferably 99.6% by mass ormore, particularly preferably 99.8% by mass or more, extremelypreferably 99.9% by mass or more, and highly preferably 99.95% by massor more, based on the total mass of the polishing liquid, from theviewpoint of easily obtaining a high polishing rate without depending ona state of irregularities in the case of polishing a surface to bepolished having irregularities and the viewpoint of easily achieving ahigh polishing rate of silicon oxide in the case of polishing a surfaceto be polished having no irregularities. The total amount of theabrasive grains, the hydroxy acid compound, and water may be 100% bymass or less than 100% by mass.

(pH)

The lower limit of the pH of the polishing liquid of the presentembodiment is preferably 1.0 or more, more preferably 1.5 or more,further preferably 2.0 or more, particularly preferably 2.2 or more,extremely preferably 2.4 or more, highly preferably 2.5 or more, evenmore preferably 3.0 or more, further preferably 3.2 or more,particularly preferably 3.4 or more, and extremely preferably more than3.4, from the viewpoint of easily achieving a sufficiently highpolishing rate of silicon oxide. The upper limit of the pH is preferably7.0 or less, more preferably 6.5 or less, further preferably 6.0 orless, particularly preferably 5.5 or less, extremely preferably 5.0 orless, highly preferably 4.5 or less, even more preferably 4.0 or less,further preferably less than 4.0, particularly preferably 3.8 or less,and extremely preferably 3.5 or less, from the viewpoint of easilyachieving a sufficiently high polishing rate of silicon oxide. Fromthese viewpoints, the pH of the polishing liquid is preferably 1.0 to7.0, more preferably 3.0 to 7.0, further preferably 3.0 to 6.0,particularly preferably 3.0 to 5.0, and extremely preferably 3.5 to 5.0.The pH of the polishing liquid is defined as the pH at a liquidtemperature of 25° C.

The pH of the polishing liquid of the present embodiment can be measuredby a pH meter (for example, Model No. PHL-40 manufactured by DenkiKagaku Keiki Co., Ltd.). For example, after performing 3-pointcalibration using a standard buffer solution (phthalate pH buffersolution, pH: 4.01; neutral phosphate pH buffer solution, pH: 6.86;borate pH buffer solution, pH: 9.18), an electrode is placed in thepolishing liquid, and the pH upon stabilization after an elapse of 3minutes or longer is measured by the measurement apparatus. The liquidtemperature of both the standard buffer solution and the polishingliquid are set to 25° C.

(Storage Form and Usage Form)

The polishing liquid of the present embodiment may be stored as aone-pack type polishing liquid containing at least abrasive grains andthe hydroxy acid compound, or as a multi-pack type (for example,two-pack type) polishing liquid set containing constituent components ofthe polishing liquid divided into a slurry (first liquid) and anadditive liquid (second liquid) such that the slurry and additive liquidare mixed to form the polishing liquid. The slurry contains, forexample, at least abrasive grains and water. The additive liquidcontains, for example, at least the hydroxy acid compound and water.

In the polishing liquid set of the present embodiment, the slurry andthe additive liquid are mixed immediately before polishing or duringpolishing to prepare the polishing liquid. Furthermore, a one-pack typepolishing liquid may be stored as a stock solution for a polishingliquid with a reduced liquid medium content, and used by dilution with aliquid medium at the time of polishing. A multi-pack type polishingliquid set may be stored as a stock solution for a slurry and a stocksolution for an additive liquid with reduced liquid medium contents, andused by dilution with a liquid medium at the time of polishing.

<Polishing Method>

A polishing method of the present embodiment includes a polishing stepof polishing a material to be polished by using the polishing liquid ofthe present embodiment. The polishing step is, for example, a step ofpolishing an insulating material (for example, an insulating materialsuch as silicon oxide) of a base substrate having the insulatingmaterial on the surface thereof by using the polishing liquid of thepresent embodiment. The polishing step is, for example, a step ofpolishing a material to be polished by a polishing member whilesupplying the polishing liquid of the present embodiment between amaterial to be polished (for example, an insulating material) and thepolishing member (such as a polishing pad). The material to be polishedmay contain an insulating material, may contain an inorganic insulatingmaterial, and may contain silicon oxide. The polishing step is, forexample, a step of flattening a base substrate having an insulatingmaterial (for example, an insulating material such as silicon oxide) onthe surface thereof by the CMP technique using a polishing liquid inwhich the content of each component, the pH, and the like are adjusted.The material to be polished may be in the form of a film (film to bepolished) and may be an insulating film such as a silicon oxide film.

The polishing step may be a step of polishing a base substrate includinga substrate having irregularities on the surface thereof, a stopperprovided on the substrate along the surface shape of the substrate, andan insulating material (for example, silicon oxide) provided on thestopper along the shape of the stopper. The polishing step may have afirst step (coarse polishing step) of polishing and removing aninsulating material until a part positioned on a convex portion of asubstrate surface in the stopper is exposed and a second step (finishingstep) of polishing and removing the stopper and the insulating materialafter the first step. The polishing liquid and the polishing method ofthe present embodiment can be used in at least one selected from thegroup consisting of the first step and the second step. The stopper maycontain silicon nitride. The stopper may be in the form of a film(stopper film) and may be a silicon nitride film.

The polishing method of the present embodiment is suitable for polishingthe base substrate having a material to be polished (for example, aninsulating material such as silicon oxide) on the surface thereof in theproduction process of a device as described below. Examples of thedevice include a discrete semiconductor such as diode, transistor,compound semiconductor, thermistor, varistor, and thyristor; a memoryelement such as DRAM (dynamic random access memory), SRAM (static randomaccess memory), EPROM (erasable programmable read-only memory), mask ROM(mask read-only memory), EEPROM (electrically erasable programmableread-only memory), and flash memory; a logic circuit element such as amicroprocessor, DSP, and ASIC; an integrated circuit element such as acompound semiconductor typified by MMIC (monolithic microwave integratedcircuit); a hybrid integrated circuit (hybrid IC) and a photoelectricconversion element such as light emitting diode and charge-coupledelement.

The polishing method of the present embodiment is particularly suitablefor flattening of a surface of a base substrate having step height(irregularities) on the surface. Examples of the base substrate includelogic semiconductor devices. The material to be polished may havesections with the concave portion or convex portion in a T-shaped orlattice-shaped fashion when viewed from above. For example, an object tobe polished having a material to be polished may be a semiconductorsubstrate having a memory cell. According to the present embodiment, aninsulating material (for example, an insulating material such as siliconoxide) provided on a surface of a semiconductor device (a DRAM, a flashmemory, or the like) including a semiconductor substrate having a memorycell can also be polished at a high rate. According to the presentembodiment, an insulating material (for example, an insulating materialsuch as silicon oxide) provided on a surface of a 3D-NAND flash memoryin which coarseness/fineness dependence property is likely to beexhibited can also be polished at a high polishing rate while securinghigh flatness.

The polishing method of the present embodiment can polish a material tobe polished having a pattern in which a ratio of a line width (L: Line)with respect to the sum of the line width and a space width (S: Space)is in the following range. The ratio of the line width may be 10% ormore, 20% or more, 30% or more, 40% or more, or 50% or more. The ratioof the line width may be 60% or less, 50% or less, 40% or less, 30% orless, or 20% or less. The sum of the line width and the space width maybe 50 μm or more, 80 μm or more, or 100 μm or more. The sum of the linewidth and the space width may be 200 μm or less, 150 μm or less, 120 μmor less, or 100 μm or less. The polishing liquid of the presentembodiment can be used in polishing of a material to be polished havinga pattern in which the ratio of the line width is in these ranges. Thepresent embodiment can provide a method for producing a polishingliquid, the method including a selection step of selecting a polishingliquid based on a polishing rate when a material to be polished (forexample, silicon oxide) having a pattern with L/S=50/50 μm is polishedand a polishing rate when a material to be polished (for example,silicon oxide) having a pattern with L/S=20/80 μm is polished. In theselection step, the polishing liquid may be selected based on the factthat the polishing rate when a material to be polished (for example,silicon oxide) having a pattern with L/S=50/50 μm is polished is 12000Å/min or more and the polishing rate when a material to be polished (forexample, silicon oxide) having a pattern with L/S=20/80 μm is polishedis 190000 Å/min or more.

The object to be polished is not limited to a base substrate havingsilicon oxide covering the entire surface, and may be a base substratefurther having silicon nitride, polycrystalline silicon, or the likeother than the silicon oxide on the surface thereof. The object to bepolished may be a base substrate in which an insulating material (forexample, an inorganic insulating material such as silicon oxide, glass,or silicon nitride), polysilicon, Al, Cu, Ti, TiN, W, Ta, TaN, or thelike is formed on a wiring board having a predetermined wiring.

As the polishing apparatus, for example, an apparatus provided with aholder for holding a base substrate, a polishing platen to which apolishing pad is attached, and a means for supplying a polishing liquidonto the polishing pad is suitable. Examples of the polishing apparatusinclude a polishing apparatus (Model No.: EPO-111, EPO-222, FREX200,FREX300, or the like) manufactured by EBARA CORPORATION and a polishingapparatus (trade name: Mirra3400, Reflexion polishing machine or thelike) manufactured by Applied Materials, Inc.

As the polishing pad, common unwoven cloth, a foamed body, an unfoamedbody, or the like can be used. As the material of the polishing pad, itis possible to use a resin such as polyurethane, an acrylic resin,polyester, an acrylic-ester copolymer, polytetrafluoroethylene,polypropylene, polyethylene, poly-4-methylpentene, cellulose, celluloseester, polyamide (for example, Nylon (trade name) and aramid),polyimide, polyimidamide, a polysiloxane copolymer, an oxirane compound,a phenolic resin, polystyrene, polycarbonate, or an epoxy resin.Particularly, from the viewpoint of easily obtaining an excellentpolishing rate and excellent flatness, the material for the polishingpad is preferably at least one selected from the group consisting of afoamed polyurethane and a non-foamed polyurethane. It is preferable thatthe polishing pad is subjected to grooving so that the polishing liquidis pooled.

Polishing conditions are not particularly limited, but the rotationspeed of the polishing platen is preferably 200 rpm (min⁻¹) or less fromthe viewpoint that the base substrate is not let out, and the pressure(processing load) to be applied to the base substrate is preferably 100kPa or less from the viewpoint of easily suppressing scratches on thepolished surface. The polishing liquid is preferably continuouslysupplied to the polishing pad with a pump or the like during polishing.The amount supplied for this is not limited, but it is preferable thatthe surface of the polishing pad is always covered with the polishingliquid.

It is preferable to sufficiently wash the base material in running waterafter the completion of polishing, then perform drying after removingdroplets, which have attached onto the base substrate, with the use of aspin dry or the like.

Polishing in this manner allows irregularities on the surface to beeliminated, and thereby a smooth surface across the entire basesubstrate can be obtained. By repeating the formation of a material tobe polished and the polishing thereof a predetermined number of times, abase substrate having desired number of layers can be produced.

The base substrate obtained in this way can be used as variouselectronic components and machine components. Specific examples thereofinclude semiconductor elements; optical glass for a photomask, a lens,or a prism; inorganic conductive films of ITO or the like; opticalintegrated circuits/optical switching elements/optical waveguidesconstituted with glass and crystalline materials; optical singlecrystals such as end faces of optical fibers and scintillators; solidlaser single crystals; sapphire substrates for blue laser LEDs;semiconductor single crystals of SiC, GaP, GaAs, or the like; glasssubstrates for magnetic discs; and magnetic heads. Examples

Hereinafter, the present invention will be described in more detail withreference to Examples. However, the present invention is not limited tothese Examples without departing from the technical idea of the presentinvention. For example, the type of materials of the polishing liquidand the blending ratio thereof may be types and ratios other than thetypes and ratios described in the present examples, and the compositionand the structure of the object to be polished may also be compositionsand structures other than the compositions and the structures describedin the present examples.

<Preparation of Abrasive Grains>

40 kg of cerium carbonate hydrate was placed in an alumina container andfired at 830° C. for 2 hours in air to obtain 20 kg of yellowish-whitepowder. The phase identification of this powder was performed by anX-ray diffi action method, and it was confirmed that this powdercontained polycrystalline cerium oxide. The particle diameter of thepowder obtained by firing was observed with a SEM and was found to be 20to 100 μm. Next, 20 kg of the cerium oxide powder was dry pulverizedusing a jet mill The cerium oxide powder after the pulverization wasobserved with a SEM, and was found to include particles containingpolycrystalline cerium oxide having a crystal boundary. Furthermore, thespecific surface area of the cerium oxide powder was 9.4 m²/g. Themeasurement of the specific surface area was performed by the BETmethod.

<Preparation of CMP Polishing Liquid>

15 kg of the aforementioned cerium oxide powder and 84.7 kg of deionizedwater were placed in a container and mixed. Furthermore, 0.3 kg of 1 Nacetic acid aqueous solution was added and stirred for 10 minutes tothereby obtain a cerium oxide mixed liquid. This cerium oxide mixedliquid was send to another container over 30 minutes. Meanwhile, in thesending pipe, the cerium oxide mixed liquid was irradiated withultrasonic wave at an ultrasonic wave frequency of 400 kHz.

CMP polishing liquids containing 1.0% by mass of the aforementionedabrasive grains, the acid components described in Tables 1 to 3 (thehydroxy acid compound and other acid components), and deionized water(remainder) were obtained.

The average particle diameter of the abrasive grains in the polishingliquid was measured using a laser diffraction/scattering type particlesize distribution analyzer (trade name: LA-920 manufactured by HORIBA,Ltd.), and the average particle diameter in any cases was found to be 90nm.

The pH of the CMP polishing liquid was measured under the followingconditions. The pH in Examples and Comparative Examples other thanComparative Example 1 was 3.5 and the pH in Comparative Example 1 was5.0.

Measurement temperature: 25° C.

Measurement apparatus: Model No. PHL-40 manufactured by Denki KagakuKeiki Co., Ltd.

Measurement method: After performing 3-point calibration using astandard buffer solution (phthalate pH buffer solution, pH: 4.01 (25°C.); neutral phosphate pH buffer solution, pH: 6.86 (25° C.); borate pHbuffer solution, pH: 9.18), an electrode was placed in the polishingliquid, and the pH upon stabilization after an elapse of 3 minutes orlonger was measured by the measurement apparatus.

An adequate amount of a ceria slurry was introduced into trade name:DelsaNano C manufactured by Beckman Coulter, Inc. and measurement wasperformed twice at 25° C. The average value of the displayed zetapotentials was obtained as the zeta potential. The zeta potential of theceria particles in the ceria slurry was +60 mV.

<Polishing Characteristic Evaluation>

(Preparation of Wafer)

A blanket wafer having a silicon oxide film on the surface thereof waspolished using the aforementioned CMP polishing liquid under thepolishing conditions below to obtain a polishing rate (blanket waferpolishing rate). The blanket wafer is a wafer that has a silicon oxidefilm having a film thickness of 1000 nm disposed on a silicon substratehaving a diameter of 200 mm.

A pattern wafer having a silicon oxide film with irregularities as afilm to be polished was polished using the aforementioned CMP polishingliquid under the polishing conditions below to obtain a polishing rate.The pattern wafer was obtained in such a manner that a silicon nitridefilm was formed as a stopper film on a part of a silicon substratehaving a diameter of 200 mm, a part of the silicon substrate on whichthe silicon nitride film was not formed was then etched at 350 nm toform a concave portion, and then a 600-nm silicon oxide film was formedon the stopper film and in the concave portion by a plasma CVD method.The pattern wafer has patterns with L/S=50/50 μm and L/S=20/80 μm.

[Polishing Conditions]

Polishing apparatus: Polishing machine for CMP Mirra 3400 (manufacturedby Applied Materials, Inc.)

Polishing pad: Porous urethane pad IC-1010 (manufactured by Rohm andHaas Japan K.K.)

Polishing pressure: 3.0 psi (20.7 kPa)

Number of revolutions of platen: 126 rpm

Number of revolutions of head: 125 rpm

Amount of CMP polishing liquid to be supplied: 200 mL/min

Polishing time: 30 seconds

(Calculation of Blanket Wafer Polishing Rate)

The film thicknesses before and after polishing of the silicon oxidefilm were measured using a light interference type film thicknessmeasuring apparatus (apparatus name: F80) manufactured by FilmetricsJapan, Inc. The film thicknesses at 79 points positioned on the line(diameter) passing through the center of the wafer with an equalinterval were measured, and an average value thereof was obtained as thefilm thickness. The polishing rate was calculated by the followingformula based on the film thicknesses before and after polishing and thepolishing time. Results are shown in Tables 1 to 3.

Polishing rate [Å/min]=(Film thickness [Å] before polishing−Filmthickness [Å] after polishing)/Polishing time [min]

(Calculation of Pattern Wafer Polishing Rate)

The film thicknesses before and after polishing of the silicon oxidefilm were measured using a light interference type film thicknessapparatus (apparatus name: Nanospec AFT-5100) manufactured byNanometrics Inc. The polishing rate was calculated by the followingformula based on the film thicknesses before and after polishing and thepolishing time. Results are shown in Tables 1 to 3.

Polishing rate [Å/min]=(Film thickness [Å] before polishing−Filmthickness [Å] after polishing)/Polishing time [min]

TABLE 1 Example 1 2 3 4 5 Hydroxy Type 2,2-Bis(hydroxymethyl)propionicacid acid Content [% by mass] 0.30 0.30 0.30 0.15 0.075 Other acid TypeGlycine Aminothiazole 3,5-Dimethylpyrazole Glycine Glycine componentContent [% by mass] 0.30 0.10 0.15 0.075 0.30 Polishing Blanket wafer8600 8950 8900 9148 9944 rate Pattern wafer 16500 18900 19000 1497114022 [Å/min] L/S = 50/50 μm Pattern wafer 26000 28400 27100 23513 19970L/S = 20/80 μm

TABLE 2 Example 6 7 8 9 Hydroxy acid Type 2,2-Bis(hydroxymethyl)DL-glyceric 2-Hydroxyisobutyric Mandelic butyric acid acid acid acidContent [% by mass] 0.30 0.30 0.30 0.30 Other acid Type Glycine GlycineGlycine Glycine component Content [% by mass] 0.30 0.30 0.30 0.30Polishing rate Blanket wafer 8800 8400 9300 3668 [Å/min] Pattern wafer19500 15100 18900 12014 L/S = 50/50 μm Pattern wafer 27000 23000 2830024158 L/S = 20/80 μm

TABLE 3 Comparative Example 1 2 3 4 5 6 7 Hydroxy Type — DL-lactic acid— Glycolic acid Malic acid DL-serine Gluconic acid acid Content [% bymass] 0.30 0.30 0.30 0.30 0.30 Other acid Type — Glycine Glycine GlycineGlycine Propionic acid Glycine component Content [% by mass] 0.30 0.300.30 0.30 0.10 0.15 Type — — Propionic acid — — — — Content [% by mass]0.30 Polishing Blanket wafer  6800 7400 6600 6300 360 7784 9338 ratePattern wafer 11000 13200 13500 12600 3400 11292 11600 [Å/min] L/S =50/50 μm Pattern wafer 15200 18000 17200 16900 11800 18674 17036 L/S =20/80 μm

It is found that, in Examples, a high polishing rate can be obtainedwithout depending on a state of irregularities in the case of polishinga surface to be polished having irregularities.

1. A polishing liquid comprising: abrasive grains containing a metaloxide; at least one hydroxy acid compound selected from the groupconsisting of a hydroxy acid having a structure represented by GeneralFormula (A1) below and a salt thereof; and water:

[In the formula, R¹¹ represents a hydrogen atom or a hydroxy group, R¹²represents a hydrogen atom, an alkyl group, or an aryl group, n11represents an integer of 0 or more, and n12 represents an integer of 0or more; however, a case where both of R¹¹ and R¹² are a hydrogen atomis excluded.]
 2. The polishing liquid according to claim 1, wherein then11 in the General Formula (A1) is 0 or
 1. 3. The polishing liquidaccording to claim 1, wherein the n12 in the General Formula (A1) is 1.4. The polishing liquid according to claim 1, wherein the hydroxy acidcompound contains at least one selected from the group consisting ofglyceric acid, 2,2-bis(hydroxymethyl)propionic acid,2,2-bis(hydroxymethyl)butyric acid, and hydroxyisobutyric acid.
 5. Thepolishing liquid according to claim 1, wherein a content of the hydroxyacid compound is 0.01 to 1.0% by mass.
 6. The polishing liquid accordingto claim 1, wherein the metal oxide contains cerium oxide.
 7. Thepolishing liquid according to claim 1, wherein a content of the abrasivegrains is 0.10 to 3.0% by mass.
 8. The polishing liquid according toclaim 1, further comprising an amino acid component.
 9. The polishingliquid according to claim 8, wherein the amino acid component containsglycine.
 10. The polishing liquid according to claim 1, furthercomprising an alkali component.
 11. The polishing liquid according toclaim 1, wherein a pH is 1.0 to 7.0.
 12. The polishing liquid accordingto claim 1, wherein a pH is 3.0 to 5.0.
 13. A polishing methodcomprising a step of polishing a material to be polished by using thepolishing liquid according to claim
 1. 14. The polishing methodaccording to claim 13, wherein the material to be polished containssilicon oxide.
 15. The polishing liquid according to claim 1, whereinthe hydroxy acid compound contains hydroxyisobutyric acid.
 16. Thepolishing liquid according to claim 1, wherein the hydroxy acid compoundcontains mandelic acid.
 17. The polishing liquid according to claim 10,wherein the alkali component contains aminothiazole.
 18. The polishingliquid according to claim 10, wherein the alkali component containsdimethylpyrazole.
 19. The polishing liquid according to claim 1, whereina ratio of a content of the hydroxy acid compound with respect to acontent of the abrasive grains is 0.60 or less.
 20. The polishing liquidaccording to claim 1, wherein a ratio of a content of the hydroxy acidcompound with respect to a content of the abrasive grains is 0.10 to0.60.